In paper machines and in paper finishing devices, vibrations constitute a major problem and, in present-day systems, when attempts are being made to achieve ever higher speeds, the vibration problems have become still more apparent than before. There are several possible sources of vibration in paper machines, and some of the most significant of them are rolls and cylinders, which comprise a very great mass revolving at a considerable speed. It is clear, of course, that when rolls are manufactured, attempts are being made to make their measurement precision as good as possible and, in addition, they are balanced in order to eliminate the vibrations.
However, present-day paper machines and paper finishing devices increasingly employ rolls provided with a soft coating, which rolls in operation may form a very significant source of vibration. Such rolls are used, for example, in on-line and off-line calenders, coating machines, size presses, supercalenders and equivalent, where said roll provided with a soft coating forms a nip with another roll. A paper web and possibly a felt, wire or equivalent is passed through the nip. When in this kind of nip roll arrangement, the seam of the wire, felt or web, considerable impurities or something else causing a noticeable change in the thickness of the web travelling through the nip, passes/pass through the nip during running, the coating must yield elastically, with the result that the coating serves as a spring that excites vibration. For example, in a size press and in a coating device of the size press type, the nip is defined by means of two rolls such that one nip roll is mounted by means of bearing housings directly on the frame structure of said device, while the opposite roll is mounted at its hearing housings on loading arms that are attached by means of articulated joints to the frame structure of the machine. In that case, the roll mounted on the loading arms in particular begins to vibrate, in which connection the coating of the soft-faced roll is deformed, with the result that the vibration increases and the roll begins to resonate. Until now, it has been necessary to take care of and to eliminate such vibrations so that, by changing the running speed of the machine, such a running speed has been sought that, at said running speed, the vibration does not grow any stronger but begins to be attenuated. The vibration problems have prevented the use of certain speeds.